Citations

Omadacycline, vancomycin, and rifampin, as well as rifampin combination therapies, were evaluated in an experimental rat model of methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis. All treatment groups had less MRSA recovered than saline-treated animals.

Abstract Introduction/Objective Molecular assays for Bartonella species are important in diagnosing infection and expediting patient treatment. Real time polymerase chain reaction (RT-PCR) using fluorescent resonance energy transfer (FRET) hybridization probes can be used to detect Bartonella species in blood and fresh/fixed tissue biopsies in RT-PCR instruments. Over time, new technologies and reagents are introduced and existing PCR primers and FRET probes must be re-validated on new platforms. This study aimed to compare the performance of a Bartonella RT-PCR assay using the sunsetting Roche LightCycler® 2.0 (Roche Diagnostics, Indianapolis, IN) and newer LightCycler® 480 RT- PCR instruments. Methods/Case Report DNA was extracted from 132 historically positive, whole organism spiked, and historically negative whole blood and formalin fixed paraffin embedded (FFPE) samples. Samples were run on the LightCycler® 2.0 using instrument specific LightCycler® FastStart DNA Master HybProbe enzyme and compared to results generated using the LightCycler® 480 and its instrument specific LightCycler® 480 Genotyping Master enzyme. During optimization, MgCl2 concentrations and thermocycling profiles were adjusted. Accuracy, specificity, inclusivity, and limit of detection studies were performed. Crossing point (Cp), melting temperature (Tm), fluorescent peak and fluorescent background values were compared between the two instruments. Results (if a Case Study enter NA) The agreement in accuracy between the LightCycler® 2.0 and the LightCycler® 480 was 100% for whole blood samples. For historically positive FFPE samples, LightCycler® 2.0 sensitivity and LightCycler® 480 sensitivity were 86% and 100%, respectively. Specificity and inclusivity of the assay were identical between the two instruments. The limit of detection in whole blood was 5-fold lower on the LightCycler® 480 (50 copies/µL) compared to the LightCycler® 2.0 (250 copies/µL). Mean Cp and fluorescent peak intensity values increased by 5.1% and 65-fold, respectively. Conclusion The study demonstrates similar performance and improved limit of detection for the Bartonella FRET hybridization probe RT-PCR assay on the LightCycler® 480 compared to the LightCycler® 2.0.

Catheter-related infections constitute an economic and mortality burden in health care. Several options are available to reduce the risk of infection, but only a few focus on preventing intraluminal infection, which occurs in long-term catheters, most often used for dialysis, prolonged treatment, or chemotherapy.

We recently reported the successful treatment of a case of periprosthetic joint infection (PJI) with phage. Phage activity against bacteria causing PJI has not been systematically evaluated.

Background: Polymerase chain reaction (PCR) is a sensitive test for diagnosing Clostridioides difficile infection (CDI) and could remain positive following resolution of CDI. The kinetics of PCR positivity following antibiotics for CDI is unknown. We studied this and whether it predicted CDI recurrence. Methods: Adults with CDI from October 2009 to May 2017 were included. Serial stool samples within 60 days of treatment were collected. Recurrent CDI was defined as diarrhea after interim symptom resolution with positive stool PCR within 56 or 90 days of treatment completion. Contingency table analysis was used to assess the risk of recurrence. Results: Fifty patients were included [median age: 51 (range = 20–86) years, 66% women]. Treatment given was metronidazole, 50% (25); vancomycin, 44% (22); both, 4% (2); and fidaxomicin, 2% (1). Median duration of treatment for all 50 patients was 14 (range = 8–60) days. The median duration of treatment in patients who got prolonged therapy (>14 days) ( n = 10) was 47 (range = 18–60) days. Median time to negative PCR was 9 (95% CI, 7–14) days from treatment initiation, which did not differ by antibiotics given ( p = 0.5). A positive PCR during or after treatment was associated with a higher risk of recurrence at 56 days ( p = 0.02) and at 90 days ( p = 0.009). Conclusion: The median time to negative PCR in CDI was 9 days from treatment initiation. The PCR positivity during or after treatment may be useful for recurrence prediction; larger studies are needed to validate these results.

Abstract Whole genome sequencing is emerging as a promising tool for the untargeted detection of a broad range of microbial species for diagnosis and analysis. However, it is logistically challenging to perform the multistep process from sample preparation to DNA amplification to sequencing and analysis within a short turnaround time. To address this challenge, we developed a digital microfluidic device for rapid whole genome amplification of low-abundance bacterial DNA and compared results with conventional in-tube DNA amplification. In this work, we chose Corynebacterium glutamicum DNA as a bacterial target for method development and optimization, as it is not a common contaminant. Sequencing was performed in a hand-held Oxford Nanopore Technologies MinION sequencer. Our results show that using an in-tube amplification approach, at least 1 pg starting DNA is needed to reach the amount required for successful sequencing within 2 h. While using a digital microfluidic device, it is possible to amplify as low as 10 fg of C. glutamicum DNA (equivalent to the amount of DNA within a single bacterial cell) within 2 h and to identify the target bacterium within 30 min of MinION sequencing100× lower than the detection limit of an in-tube amplification approach. We demonstrate the detection of C. glutamicum DNA in a mock community DNA sample and characterize the limit of bacterial detection in the presence of human cells. This approach can be used to identify microbes with minute amounts of genetic material in samples depleted of human cells within 3 h.

Abstract We studied the performance of an algorithm combining multiplex polymerase chain reaction with phenotypic detection of extended-spectrum β-lactamases and carbapenemases directly from positive blood culture bottles in patients with gram-negative bacteremia and found good concordance with routine cultures. Such an algorithm may be a tool to improve time to optimal therapy in patients with gram-negative bacteremia.

Antimicrobial susceptibility testing (AST) is routinely used to establish predictive antibiotic resistance metrics to guide the treatment of bacterial pathogens. Recently, a novel phenotype termed “bicarbonate (NaHCO3)-responsiveness” was identified in a relatively high frequency of clinical MRSA strains, wherein isolates demonstrate in vitro “susceptibility” to standard β-lactams (oxacillin [OXA]; cefazolin [CFZ]) in the presence of NaHCO3, and in vivo susceptibility to these β-lactams in experimental endocarditis models. We investigated whether a targeted phenotypic-genotypic screening of MRSA could rule in or rule out NaHCO3 susceptibility upfront. We studied 30 well-characterized clinical MRSA bloodstream isolates, including 15 MIC-susceptible to CFZ and OXA in NaHCO3-supplemented Mueller–Hinton Broth (MHB); and 15 MIC-resistant to both β-lactams in this media. Using a two-tiered strategy, isolates were first screened by standard disk diffusion for susceptibility to a combination of amoxicillin-clavulanate [AMC]. Isolates then underwent genomic sequence typing: MLST (clonal complex [CC]); agr; SCCmec; and mecA promoter and coding region. The combination of AMC disk susceptibility testing plus mecA and spa genotyping was able to predict MRSA strains that were more or less likely to be NaHCO3-responsive in vitro, with a high degree of sensitivity and specificity. Validation of this screening algorithm was performed in six strains from the overall cohort using an ex vivo model of endocarditis. This ex vivo model recapitulated the in vitro predictions of NaHCO3-responsiveness vs. nonresponsiveness above in five of the six strains.

Abstract Urinary tract infections (UTIs) are among the most common bacterial infections in the United States and are a major driver of antibiotic use, both appropriate and inappropriate, across healthcare settings. Novel UTI diagnostics are a strategy that might enable better UTI treatment. Members of the Antibacterial Resistance Leadership Group Laboratory Center and the Infectious Diseases Society of America Diagnostics Committee convened to envision ideal future UTI diagnostics, with a view towards improving delivery of healthcare, patient outcomes and experiences, and antibiotic use, addressing which types of UTI diagnostics are needed and how companies might approach development of novel UTI diagnostics.

In total, 50 Escherichia coli bloodstream isolates from the clinical laboratory and 12 E. coli isolates referred for pulsed-field gel electrophoresis (PFGE) were sequenced, assessed for clonality using core genome multilocus sequence typing (cgMLST), and evaluated for genomic susceptibility predictions using ARESdb. Results of sequence typing using whole-genome sequencing (WGS)-based MLST and sequence type (ST)-specific PCR were identical.